Until now, the refractory material used in electromagnetic pumps for molten aluminum by applicant was a fibrous refractory concrete, such as the concrete described in French Pat. No. 2,203,788, filed Oct. 24, 1972 by applicant.
This fibrous concrete was very resistant to thermal shock as well as to corrosion by aluminum, but it had weak mechanical properties. It followed that, during the cleaning of the pump, i.e., of the turn 7 with reference to the above-mentioned Patent Application Ser. No. 79-14585, the concrete which was too soft eroded with the metal tools used. Thus, this concrete had poor abrasion resistance.
It is an object of the invention to overcome this drawback.
More specifically, it is an object of the invention to obtain a refractory material which has not only high resistance to air oxidation at high temperature, to the corrosive action of aluminum and its alloys in the molten state, to thermal shocks and thermal fatigue, but which moreover possesses the property of being easily formed and machined, while retaining high abrasion resistance.
According to the invention there is provided a refractory material constituted by an aggregate bonded by a cement and in which the aggregate is constituted by silicon nitride.
Preferably the silicon nitride entering into the composition of the refractory material according to the invention is present in a proportion in the range between 50% and 90% of the total weight of the final product, and in a preferred embodiment, the proportion of silicon nitride is between 70% and 80% of the total weight of the final product.
Preferably, the silicon nitride entering into the composition of the refractory material is a silicon nitride sintered by reaction.